Low-crystallinity polyester chip for producing molded film and preparation method of low-crystallinity polyester chip

Abstract

The invention discloses a low-crystallinity polyester chip for producing a molded film and a preparation method of the low-crystallinity polyester chip, which are characterized in that a semi-continuous production synthesis device is adopted, terephthalic acid and ethylene glycol are added in an esterification reaction to generate an ester intermediate, and the ester intermediate is used as a target polyester chip skeleton structure to participate in a subsequent reaction; isophthalic acid, diethylene glycol, neopentyl glycol and tetramethyl cyclobutanediol are added in the secondary esterification reaction, and ester intermediates are also generated in the presence of deionized water and serve as a target polyester chip skeleton modified structure to participate in the subsequent reaction; mixing the primary esterification reaction product with the secondary esterification reaction product, continuously reacting to generate a mixture of ester intermediates, adding a titanium catalyst, introducing the mixture into a polycondensation reaction kettle through a melt filter after a certain temperature is reached, and synthesizing a target high-molecular polymer by controlling the temperature, the vacuum degree and the stirring power. And enabling the high-temperature melt to pass through a casting head, underwater pelletizing equipment and drying equipment to obtain the low-crystallinity polyester chip for producing the molded film.

Description

Technical Field

[0001] The invention relates to a polyester chip and a preparation method thereof, in particular to a low-crystallinity polyester chip for producing a molded film and a preparation method thereof. Background Art

[0002] High-gloss molded polyester film is mainly used in the field of packaging laser anti-counterfeiting. The molded film materials currently on the market include PVC, BOPET, BOPP, etc. Among them, BOPET has good heat resistance, high dimensional stability, relatively high gloss and transmittance, and high brightness after aluminum plating, making it more suitable for molding. However, since conventional unmodified PET polyester itself has a high degree of crystallinity, it is difficult to control the crystallization after film formation, which affects the transmittance of the product and cannot be directly used for nickel plate molding. Therefore, the currently widely used BOPET polyester molded film must be produced through offline coating, and a layer of molded information layer is coated on the surface of the polyester film. The offline coating process of molded products on the current market has high production costs and high process risks. There is an urgent need for a low-crystallinity, high-brightness polyester chip as the BOPET surface layer to replace the conventional offline coating process. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a low-crystallinity polyester chip for producing a molded film and a preparation method thereof. The product is applied to the surface layer of a three-layer co-extruded molded film and is used as a functional layer of the product to replace the conventional coating process. It has high light transmittance and is easy to mold at low temperature. Compared with the coated film, the film after molding is dimensionally stable and has better weather resistance. In addition, the multi-layer co-extruded material of the product is PET, which has a higher recycling rate in the later stage compared with PVC, PP, etc., and has good environmental protection characteristics.

[0004] In order to achieve the above excellent product characteristics and to make up for the defects of existing processing technology and materials, the technical solution adopted by the present invention is: a preparation method of low crystallinity polyester chips for producing molded films, comprising the following steps:

[0005] ① Add a certain amount of ethylene glycol to a beating kettle, and then add a certain amount of terephthalic acid solid powder to prepare a viscous slurry, and then pump it into an esterification reaction kettle through a slurry supply pump to start the first step of esterification reaction; wherein the molar ratio of terephthalic acid to the total acid in the esterification reaction is 75%-85%, and the molar ratio of ethylene glycol to the total alcohol in the esterification reaction is 75%-85%;

[0006] The reaction products are as follows:

[0007]

[0008] Where m represents the number of monomer polymerization chains, which is generally 3-5.

[0009] ② Add a certain amount of diethylene glycol, neopentyl glycol and tetramethylcyclobutanediol to the feed port of the diesterification reactor, and add an appropriate amount of deionized water, the amount of deionized water is sufficient to ensure that the diesterification reactor can be stirred normally; after stirring, add a certain amount of isophthalic acid, cover the feed port, start heating, and carry out the second step of esterification reaction; wherein the molar ratio of isophthalic acid to the total acid of the esterification reaction is 15%-25%, the molar ratio of diethylene glycol to the total alcohol of the esterification reaction is 5%-8%, the molar ratio of neopentyl glycol to the total alcohol of the esterification reaction is 6%-10%, and the molar ratio of tetramethylcyclobutanediol to the total alcohol of the esterification reaction is 4%-7%.

[0010] The reaction products are as follows:

[0011]

[0012] Where x:y:z=(0.86-2.5):(0.71-2.0):1

[0013] ③ After the raw materials added in ① and ② have reacted completely, the esterification product generated in the reaction in ① is introduced into the diesterification reaction kettle through a pipeline, mixed with the second step esterification product in ②, the diesterification kettle is started for stirring, and the temperature is raised to 230-250°C, and an appropriate amount of the catalyst purchased from the auxiliary agent port is added; the molar ratio of the total acid to the total alcohol in the two esterification reactions is 1: (1.15-1.35);

[0014] ④ When the reaction in step ③ is completed and the slurry temperature is stabilized to 230-250°C, the materials in the diesterification reactor are pressed into the polycondensation reactor by high-purity nitrogen through a 15-25μm stainless steel filter;

[0015] ⑤ After the mixed slurry enters the polycondensation kettle, the material temperature is raised to 245-255°C, and the temperature is raised to draw a low vacuum; the reaction temperature is controlled at 275-285°C, and a negative pressure polymerization reaction is carried out, and the vacuum degree is required to be ≤30Pa. At the final temperature of 275-285°C, the stirring polycondensation current and power are controlled by the equipment to synthesize a high-viscosity polyester chip melt with a characteristic viscosity of 0.700-0.720dl / g, and then passed through a casting head, an underwater pelletizer, a dryer, and a vibrating screen to finally obtain a low-crystallinity polyester chip for the production of molded film.

[0016] The method for preparing low-crystallinity polyester chips for producing molded films is characterized in that the molar ratio of the alcohol acid in the first esterification step and the molar ratio of the alcohol acid in the second esterification step are both required to be greater than 1 to ensure complete acid esterification; the first esterification step requires the reaction temperature to be controlled at 245-265°C, and the second esterification step requires the temperature to be first raised to 100-110°C and kept constant for 30 minutes, and then the temperature is raised to 220-230°C.

[0017] The catalyst is a titanium catalyst, and the added amount is 100-300ppm of the theoretical polyester chip output.

[0018] The low crystallinity polyester chips prepared by the above preparation method are used for producing molded films.

[0019] The beneficial effects of the present invention are:

[0020] 1. Through two-step simultaneous esterification reaction, the target monomer can be formed according to the reaction preset. The first step of esterification reaction forms the initial skeleton of the polymer, and the second step of esterification reaction forms a modified polyester chain segment, which is convenient for the material to be mixed and connected to the polymer skeleton in the polycondensation reaction stage, so that a uniform polymer chain can be formed to ensure the consistency and uniformity of product characteristics;

[0021] 2. By introducing diethylene glycol to replace part of ethylene glycol, the fluidity of polyester chips during film processing can be greatly improved, providing fluidity guarantee for subsequent molding deformation at a lower temperature and improving molding processing efficiency;

[0022] 3. By introducing an appropriate amount of neopentyl glycol and isophthalic acid and utilizing their synergistic effect, the melting point of the polyester chips is greatly reduced, providing the necessary structural basis for low-temperature molding. This is also a key factor in replacing traditional molding materials such as PVC and PP.

[0023] 4. By introducing a small amount of tetramethylcyclobutanediol, the crystallization problem in the subsequent film drawing process can be greatly improved. By forming local chaos in the chain segments, the crystallization tendency of the product in the film drawing and shaping process is reduced, and a low degree of crystallinity is maintained, which provides a guarantee for the high light transmittance of the molded film. At the same time, tetramethylcyclobutanediol, due to its special cyclic multi-branched structure, further improves the heat shock resistance of the molded film during use. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] The method for preparing low crystallinity polyester chips for producing molded films of the present invention comprises the following steps:

[0026] ① Add a certain amount of ethylene glycol to a beating kettle, and then add a certain amount of terephthalic acid solid powder to prepare a viscous slurry, and then pump it into an esterification reaction kettle through a slurry supply pump to start the first step of esterification reaction; wherein the molar ratio of terephthalic acid to the total acid in the esterification reaction is 75%-85%, and the molar ratio of ethylene glycol to the total alcohol in the esterification reaction is 75%-85%;

[0027] ② Add a certain amount of diethylene glycol, neopentyl glycol and tetramethylcyclobutanediol to the feed port of the diesterification reactor, and add an appropriate amount of deionized water, the amount of deionized water is sufficient to ensure that the diesterification reactor can be stirred normally; after stirring, add a certain amount of isophthalic acid, cover the feed port, start heating, and carry out the second step of esterification reaction; wherein the molar ratio of isophthalic acid to the total acid of the esterification reaction is 15%-25%, the molar ratio of diethylene glycol to the total alcohol of the esterification reaction is 5%-8%, the molar ratio of neopentyl glycol to the total alcohol of the esterification reaction is 6%-10%, and the molar ratio of tetramethylcyclobutanediol to the total alcohol of the esterification reaction is 4%-7%.

[0028] ③ After the raw materials added in ① and ② have reacted completely, the esterification product generated in the reaction in ① is introduced into the diesterification reaction kettle through a pipeline, mixed with the second step esterification product in ②, the diesterification kettle is started for stirring, and the temperature is raised to 230-250°C, and an appropriate amount of the catalyst purchased from the auxiliary agent port is added; the molar ratio of the total acid to the total alcohol in the two esterification reactions is 1: (1.15-1.35);

[0029] ④ When the reaction in step ③ is completed and the slurry temperature is stabilized to 230-250°C, the materials in the diesterification reactor are pressed into the polycondensation reactor by high-purity nitrogen through a 15-25μm stainless steel filter;

[0030] ④ After the mixed slurry enters the polycondensation kettle, the material temperature is raised to 245-255°C, and the temperature is raised to draw a low vacuum; the reaction temperature is controlled at 275-285°C, and a negative pressure polymerization reaction is carried out, and the vacuum degree is required to be ≤30Pa. At the final temperature of 275-285°C, the stirring polycondensation current and power are controlled by the equipment to synthesize a high-viscosity polyester chip melt with a characteristic viscosity of 0.700-0.720dl / g, and then passed through a casting head, an underwater pelletizer, a dryer, and a vibrating screen to finally obtain a low-crystallinity polyester chip for the production of molded film.

[0031] The molar ratio of alcohol and acid in the first step esterification and the second step esterification reaction is required to be greater than 1 to ensure complete esterification; the first step esterification reaction requires the reaction temperature to be controlled at 245-265°C, and the second step esterification reaction requires first heating to 100-110°C and keeping the temperature constant for 30 minutes, and then raising the temperature to 220-230°C.

[0032] The catalyst used in the synthesis process is a titanium catalyst, and the added amount is 100-300ppm of the theoretical polyester chip output.

[0033] The low crystallinity polyester chips for producing molded films are finally obtained through the above preparation method.

[0034] Compared with the molded film produced by the patented product of the present invention, the molded film produced by the conventional process has the following shortcomings:

[0035] 1. The processing technology is complicated during the film drawing process, and the molded functional layer needs to be realized through online coating, which is difficult to achieve;

[0036] 2. Using conventional PET polyester chips as the molding layer, the crystallinity is high during the film drawing and shaping process, the film surface is white, and the light transmittance is low, which makes it difficult to be applied to the field of high-end laser labels;

[0037] 3. The molded film produced by using conventional PET polyester chips has a high melting point of the surface material, and it is difficult to achieve low-temperature molding, and the energy consumption is higher;

[0038] 3. The molded film produced using conventional PET polyester chips is prone to brittle cracking at high temperatures and has poor thermal shock resistance due to the lack of modified alcohols and acids.

[0039] It is necessary to implement synchronous control of various indicators in the synthesis of the product of the present invention:

[0040] 1. Stable chain structure and uniform performance

[0041] By controlling the two-step simultaneous esterification reaction, the target monomer can be formed according to the reaction preset, wherein the first step of esterification reaction forms the initial skeleton of the polymer, and the second step of esterification reaction forms the modified polyester chain segment, which is convenient for the material to be mixed and then connected to the polymer skeleton in the polycondensation reaction stage, so that a uniform polymer chain can be formed, ensuring the consistency and uniformity of product characteristics;

[0042] 2. Excellent film drawing effect

[0043] By introducing diethylene glycol to replace traditional ethylene glycol, the fluidity of polyester chips during film processing can be greatly improved, providing fluidity guarantee for subsequent molding at lower temperatures;

[0044] 3. Lower molding temperature:

[0045] By introducing an appropriate amount of neopentyl glycol and isophthalic acid and utilizing their synergistic effect, the melting point of the polyester chips can be greatly reduced from the conventional 260°C to a minimum of about 150°C, providing the necessary conditions for low-temperature molding and facilitating the early promotion of the product.

[0046] 4. Low crystallinity and excellent heat shock resistance:

[0047] By introducing a small amount of tetramethylcyclobutanediol, the crystallization problem in the subsequent film drawing process can be greatly improved. By forming local chaos in the chain segments, the crystallization tendency of the product in the film drawing and shaping process is reduced, and a low degree of crystallinity is maintained, which provides a guarantee for the high light transmittance of the molded film. At the same time, tetramethylcyclobutanediol, due to its special cyclic multi-branched structure, further improves the heat shock resistance of the molded film during use.

[0048] Example 1

[0049] ① Add 750 kg of ethylene glycol to the pulping kettle, and then add 1600 kg of terephthalic acid solid powder to prepare a viscous slurry, and then pump it into an esterification reactor through a slurry pump to start the first step of esterification reaction. When the esterification water output reaches 330 kg, the first step of esterification is considered to be completed;

[0050] ② Add 110Kg of diethylene glycol, 125Kg of neopentyl glycol and 110Kg of tetramethylcyclobutanediol to the diesterification reactor feed port, add 200Kg of deionized water, start the diesterification reactor for stirring, then add 400Kg of isophthalic acid, cover the feed port, start heating, first raise the temperature to 105°C, and after 30 minutes, raise the temperature to 230°C to carry out the second step of esterification reaction. When the esterification water output reaches 280Kg, the second step of esterification is considered to be completed;

[0051] ③ After the raw materials added in ① and ② have reacted completely, the esterification product generated in the reaction in ① is introduced into the diesterification reaction kettle through a pipeline, and mixed with the second step esterification product in ②. The diesterification kettle is started for stirring, and the temperature is raised to 240°C, and 480g of titanium catalyst is added from the auxiliary agent port;

[0052] ④ After the reaction in step ③ is completed and the slurry temperature is stabilized to 240°C, the materials in the diesterification reactor are pressed into the polycondensation reactor by high-purity nitrogen through a 25μm stainless steel filter;

[0053] ④ After the mixed slurry enters the polycondensation reactor, the material temperature is raised to 250°C, and the temperature is raised to draw a low vacuum; the final reaction temperature is 282°C, and a negative pressure polymerization reaction is carried out with a vacuum degree of 30Pa. After 4.5 hours, the preset power is reached and the discharge is carried out. The tested product characteristic viscosity is 0.718dl / g.

[0054] According to the method of steps ① to ④, implement other 2-4 examples. The specific data is shown in Table 1:

[0055] Table 1:

[0056]

[0057]

[0058] The low-crystallinity polyester chips used in the present invention for producing molded films have lower molding temperature, better heat shock resistance, and more superior economic applicability than conventional polyester chips for molded films, and are excellent alternative products for improving film drawing technology and expanding downstream applications.

[0059] The following is explained in conjunction with specific embodiments:

[0060] The low crystallinity polyester chips used to produce the molded film in Examples 1-4 above were tested for their intrinsic viscosity, melting point and crystallinity. The polyester chips of the present invention were processed into 25 μm films through an ABC three-layer co-extrusion BOPET film production line, with 15% A-side addition, a core layer of fiber gloss (provided by Yizheng Chemical Fiber), and an anti-adhesion layer of a high-gloss polyester chip containing an opening agent (a high-gloss product of grade F02 provided by Huaxinying Company). The light transmittance of the films was tested, and the test results are summarized in Table 2 below:

[0061] Table 2:

[0062]

[0063] The embodiments described above are only used to illustrate the technical ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The patent scope of the present invention cannot be limited only by this embodiment, that is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the patent scope of the present invention.

Claims

1. A method for preparing a low-crystallinity polyester chip for producing a molded film, characterized in that: The following steps are involved: ① Add a certain amount of ethylene glycol to a beating kettle, and then add a certain amount of terephthalic acid solid powder to prepare a viscous slurry, and then pump it into an esterification reaction kettle through a slurry supply pump to start the first step of esterification reaction; wherein the molar ratio of terephthalic acid to the total acid in the esterification reaction is 75%-85%, and the molar ratio of ethylene glycol to the total alcohol in the esterification reaction is 75%-85%; ② Add a certain amount of diethylene glycol, neopentyl glycol and tetramethylcyclobutanediol to the feed port of the diesterification reactor, and add an appropriate amount of deionized water. The amount of deionized water is sufficient to ensure that the stirring of the diesterification reactor can be started normally; after the stirring is started, add a certain amount of isophthalic acid, cover the feed port, start heating, and carry out the second step of esterification reaction; The molar ratio of isophthalic acid to the total acid in the esterification reaction is 15%-25%, the molar ratio of diethylene glycol to the total alcohol in the esterification reaction is 5%-8%, the molar ratio of neopentyl glycol to the total alcohol in the esterification reaction is 6%-10%, and the molar ratio of tetramethylcyclobutanediol to the total alcohol in the esterification reaction is 4%-7%. ③ After the raw materials added in ① and ② have reacted completely, the esterification product generated in the reaction in ① is introduced into the diesterification reaction kettle through a pipeline, mixed with the second step esterification product in ②, the diesterification kettle is started for stirring, and the temperature is raised to 230-250℃, and the catalyst is added from the auxiliary agent port; ④ When the reaction in step ③ is completed and the slurry temperature is stabilized to 230-250°C, the materials in the diesterification reactor are pressed into the polycondensation reactor by high-purity nitrogen through a 15-25μm stainless steel filter; ④ After the mixed slurry enters the polycondensation kettle, the material temperature is raised to 245-255°C, and the temperature is raised to draw a low vacuum; the reaction temperature is controlled at 275-285°C, and a negative pressure polymerization reaction is carried out, requiring the vacuum degree to be ≤30Pa. At the final temperature of 275-285°C, the stirring polycondensation current and power are controlled to synthesize a high-viscosity polyester chip melt with a characteristic viscosity of 0.700-0.720dl / g, and then passed through a casting head, an underwater pelletizer, a dryer, and a vibrating screen to finally obtain a low-crystallinity polyester chip for the production of molded film.

2. The method for preparing low crystallinity polyester chips for producing molded films according to claim 1, characterized in that: The molar ratio of alcohol and acid in the first step esterification and the second step esterification reaction is required to be greater than 1 to ensure complete acid esterification.

3. The method for preparing low crystallinity polyester chips for producing molded films according to claim 2, characterized in that: The molar ratio of total acid to total alcohol in the two esterification reactions is 1:(1.15-1.35).

4. The method for preparing low crystallinity polyester chips for producing molded films according to claim 1, characterized in that: The temperature of the first step esterification reaction is controlled at 245-265°C, and the temperature of the second step esterification reaction is first raised to 100-110°C and kept constant for 30 minutes, and then the temperature is raised to 220-230°C.

5. The method for preparing low crystallinity polyester chips for producing molded films according to claim 1, characterized in that: The catalyst is a titanium catalyst, and the added amount is 100-300ppm of the theoretical polyester chip output.

6. Low crystallinity polyester chips for producing molded films obtained by the preparation method according to any one of claims 1 to 5.

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